plucky (3) MPI_Neighbor_alltoallv.3.gz

Provided by: openmpi-doc_5.0.7-1_all bug

SYNTAX

   C Syntax
          #include <mpi.h>

          int MPI_Neighbor_alltoallv(const void *sendbuf, const int sendcounts[],
               const int sdispls[], MPI_Datatype sendtype,
               void *recvbuf, const int recvcounts[],
               const int rdispls[], MPI_Datatype recvtype, MPI_Comm comm)

          int MPI_Ineighbor_alltoallv(const void *sendbuf, const int sendcounts[],
               const int sdispls[], MPI_Datatype sendtype,
               void *recvbuf, const int recvcounts[],
               const int rdispls[], MPI_Datatype recvtype, MPI_Comm comm,
               MPI_Request *request)

          int MPI_Neighbor_alltoallv_init(const void *sendbuf, const int sendcounts[],
               const int sdispls[], MPI_Datatype sendtype,
               void *recvbuf, const int recvcounts[],
               const int rdispls[], MPI_Datatype recvtype, MPI_Comm comm,
               MPI_Info info, MPI_Request *request)

   Fortran Syntax
          USE MPI
          ! or the older form: INCLUDE 'mpif.h'
          MPI_NEIGHBOR_ALLTOALLV(SENDBUF, SENDCOUNTS, SDISPLS, SENDTYPE,
               RECVBUF, RECVCOUNTS, RDISPLS, RECVTYPE, COMM, IERROR)

               <type>  SENDBUF(*), RECVBUF(*)
               INTEGER SENDCOUNTS(*), SDISPLS(*), SENDTYPE
               INTEGER RECVCOUNTS(*), RDISPLS(*), RECVTYPE
               INTEGER COMM, IERROR

          MPI_INEIGHBOR_ALLTOALLV(SENDBUF, SENDCOUNTS, SDISPLS, SENDTYPE,
               RECVBUF, RECVCOUNTS, RDISPLS, RECVTYPE, COMM, REQUEST, IERROR)

               <type>  SENDBUF(*), RECVBUF(*)
               INTEGER SENDCOUNTS(*), SDISPLS(*), SENDTYPE
               INTEGER RECVCOUNTS(*), RDISPLS(*), RECVTYPE
               INTEGER COMM, REQUEST, IERROR

          MPI_NEIGHBOR_ALLTOALLV_INIT(SENDBUF, SENDCOUNTS, SDISPLS, SENDTYPE,
               RECVBUF, RECVCOUNTS, RDISPLS, RECVTYPE, COMM, INFO, REQUEST, IERROR)

               <type>  SENDBUF(*), RECVBUF(*)
               INTEGER SENDCOUNTS(*), SDISPLS(*), SENDTYPE
               INTEGER RECVCOUNTS(*), RDISPLS(*), RECVTYPE
               INTEGER COMM, INFO, REQUEST, IERROR

   Fortran 2008 Syntax
          USE mpi_f08
          MPI_Neighbor_alltoallv(sendbuf, sendcounts, sdispls, sendtype, recvbuf,
                       recvcounts, rdispls, recvtype, comm, ierror)

               TYPE(*), DIMENSION(..), INTENT(IN) :: sendbuf
               TYPE(*), DIMENSION(..) :: recvbuf
               INTEGER, INTENT(IN) :: sendcounts(*), sdispls(*), recvcounts(*),
               rdispls(*)
               TYPE(MPI_Datatype), INTENT(IN) :: sendtype, recvtype
               TYPE(MPI_Comm), INTENT(IN) :: comm
               INTEGER, OPTIONAL, INTENT(OUT) :: ierror

          MPI_Ineighbor_alltoallv(sendbuf, sendcounts, sdispls, sendtype, recvbuf,
                       recvcounts, rdispls, recvtype, comm, request, ierror)

               TYPE(*), DIMENSION(..), INTENT(IN), ASYNCHRONOUS :: sendbuf
               TYPE(*), DIMENSION(..), ASYNCHRONOUS :: recvbuf
               INTEGER, INTENT(IN), ASYNCHRONOUS :: sendcounts(*), sdispls(*),
               recvcounts(*), rdispls(*)
               TYPE(MPI_Datatype), INTENT(IN) :: sendtype, recvtype
               TYPE(MPI_Comm), INTENT(IN) :: comm
               TYPE(MPI_Request), INTENT(OUT) :: request
               INTEGER, OPTIONAL, INTENT(OUT) :: ierror

          MPI_Neighbor_alltoallv_init(sendbuf, sendcounts, sdispls, sendtype, recvbuf,
                       recvcounts, rdispls, recvtype, comm, info, request, ierror)

               TYPE(*), DIMENSION(..), INTENT(IN), ASYNCHRONOUS :: sendbuf
               TYPE(*), DIMENSION(..), ASYNCHRONOUS :: recvbuf
               INTEGER, INTENT(IN), ASYNCHRONOUS :: sendcounts(*), sdispls(*),
               recvcounts(*), rdispls(*)
               TYPE(MPI_Datatype), INTENT(IN) :: sendtype, recvtype
               TYPE(MPI_Comm), INTENT(IN) :: comm
               TYPE(MPI_Info), INTENT(IN) :: info
               TYPE(MPI_Request), INTENT(OUT) :: request
               INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT PARAMETERS

sendbuf: Starting address of send buffer.

       • sendcounts: Integer array, where entry i specifies the number of elements to send to neighbor i.

       • sdispls: Integer array, where entry i specifies the displacement (offset  from  sendbuf,  in  units  of
         sendtype) from which to send data to neighbor i.

       • sendtype: Datatype of send buffer elements.

       • recvcounts: Integer array, where entry j specifies the number of elements to receive from neighbor j.

       • rdispls:  Integer  array,  where  entry  j specifies the displacement (offset from recvbuf, in units of
         recvtype) to which data from neighbor j should be written.

       • recvtype: Datatype of receive buffer elements.

       • comm: Communicator over which data is to be exchanged.

       • info: Info (handle, persistent only).

OUTPUT PARAMETERS

recvbuf: Address of receive buffer.

       • request: Request (handle, non-blocking only).

       • ierror: Fortran only: Error status.

DESCRIPTION

       MPI_Neighbor_alltoallv is a generalized collective operation in which all  processes  send  data  to  and
       receive  data  from  all  neighbors. It adds flexibility to MPI_Neighbor_alltoall by allowing the user to
       specify data to send and receive vector-style (via a displacement and element count).  The  operation  of
       this  routine  can  be  thought  of  as  follows,  where  each process performs 2n (n being the number of
       neighbors in to topology of communicator comm) independent point-to-point communications.  The  neighbors
       and buffer layout are determined by the topology of comm.

          MPI_Cart_get(comm, maxdims, dims, periods, coords);
          for (dim = 0, i = 0 ; dim < dims ; ++dim) {
              MPI_Cart_shift(comm, dim, 1, &r0, &r1);
              MPI_Isend(sendbuf + sdispls[i]  * extent(sendtype),
                        sendcount, sendtype, r0, ..., comm, ...);
              MPI_Irecv(recvbuf + rdispls[i] * extent(recvtype),
                        recvcount, recvtype, r0, ..., comm, ...);
              ++i;
              MPI_Isend(sendbuf + sdispls[i] * extent(sendtype),
                        sendcount, sendtype, r1, ..., comm, &req[i]);
              MPI_Irecv(recvbuf + rdispls[i] * extent(recvtype),
                        recvcount, recvtype, r1, ..., comm, ...);
              ++i;
          }

       Process  j  sends  the  k-th  block of its local sendbuf to neighbor k, which places the data in the j-th
       block of its local recvbuf.

       When a pair of processes exchanges data, each may pass different element count and datatype arguments  so
       long  as  the  sender  specifies  the  same  amount of data to send (in bytes) as the receiver expects to
       receive.

       Note that process i may send a different amount of data to process j than it  receives  from  process  j.
       Also, a process may send entirely different amounts of data to different processes in the communicator.

NEIGHBOR ORDERING

       For  a  distributed  graph topology, created with MPI_Dist_graph_create, the sequence of neighbors in the
       send and receive buffers at each process is defined as the sequence returned by  MPI_Dist_graph_neighbors
       for  destinations and sources, respectively. For a general graph topology, created with MPI_Graph_create,
       the order of neighbors in the send and receive buffers  is  defined  as  the  sequence  of  neighbors  as
       returned  by  MPI_Graph_neighbors. Note that general graph topologies should generally be replaced by the
       distributed graph topologies.

       For a Cartesian topology, created with MPI_Cart_create, the sequence of neighbors in the send and receive
       buffers  at  each  process  is  defined  by  order  of the dimensions, first the neighbor in the negative
       direction and then in the positive direction with displacement 1. The numbers of sources and destinations
       in  the  communication routines are 2*ndims with ndims defined in MPI_Cart_create. If a neighbor does not
       exist, i.e., at the border of a Cartesian topology in the case of a non-periodic virtual  grid  dimension
       (i.e., periods[…]==false), then this neighbor is defined to be MPI_PROC_NULL.

       If  a  neighbor  in any of the functions is MPI_PROC_NULL, then the neighborhood collective communication
       behaves like a point-to-point communication with MPI_PROC_NULL in this direction. That is, the buffer  is
       still part of the sequence of neighbors but it is neither communicated nor updated.

NOTES

       The MPI_IN_PLACE option for sendbuf is not meaningful for this operation.

       The specification of counts and displacements should not cause any location to be written more than once.

       All  arguments on all processes are significant. The comm argument, in particular, must describe the same
       communicator on all processes.

       The offsets of sdispls and rdispls are measured in units of sendtype and recvtype, respectively.  Compare
       this to MPI_Neighbor_alltoallw, where these offsets are measured in bytes.

ERRORS

       Almost  all  MPI  routines  return  an  error  value; C routines as the return result of the function and
       Fortran routines in the last argument.

       Before the error value is returned, the current MPI  error  handler  associated  with  the  communication
       object  (e.g.,  communicator, window, file) is called.  If no communication object is associated with the
       MPI call, then the call is considered attached to MPI_COMM_SELF and will call the  associated  MPI  error
       handler.   When   MPI_COMM_SELF   is   not  initialized  (i.e.,  before  MPI_Init/MPI_Init_thread,  after
       MPI_Finalize, or when using the Sessions Model exclusively) the error raises the initial  error  handler.
       The  initial  error handler can be changed by calling MPI_Comm_set_errhandler on MPI_COMM_SELF when using
       the World model, or the mpi_initial_errhandler CLI argument to mpiexec or info  key  to  MPI_Comm_spawn/‐
       MPI_Comm_spawn_multiple.   If no other appropriate error handler has been set, then the MPI_ERRORS_RETURN
       error handler is called for MPI I/O functions and the MPI_ERRORS_ABORT error handler is  called  for  all
       other MPI functions.

       Open MPI includes three predefined error handlers that can be used:

       • MPI_ERRORS_ARE_FATAL Causes the program to abort all connected MPI processes.

       • MPI_ERRORS_ABORT An error handler that can be invoked on a communicator, window, file, or session. When
         called on a communicator, it acts as if MPI_Abort was called on  that  communicator.  If  called  on  a
         window  or file, acts as if MPI_Abort was called on a communicator containing the group of processes in
         the corresponding window or file. If called on a session, aborts only the local process.

       • MPI_ERRORS_RETURN Returns an error code to the application.

       MPI applications can also implement their own error handlers by calling:

       • MPI_Comm_create_errhandler then MPI_Comm_set_errhandlerMPI_File_create_errhandler then MPI_File_set_errhandlerMPI_Session_create_errhandler then MPI_Session_set_errhandler or at MPI_Session_initMPI_Win_create_errhandler then MPI_Win_set_errhandler

       Note that MPI does not guarantee that an MPI program can continue past an error.

       See the MPI man page for a full list of MPI error codes.

       See the Error Handling section of the MPI-3.1 standard for more information.

       SEE ALSO:MPI_Neighbor_alltoallMPI_Neighbor_alltoallwMPI_Cart_createMPI_Graph_createMPI_Dist_graph_create

       2003-2025, The Open MPI Community

                                                  Feb 17, 2025                        MPI_INEIGHBOR_ALLTOALLV(3)